Photoconductive elements containing polymeric binders

ABSTRACT

Photoconductive elements containing a photoconductor and a binder for the photoconductor comprising a poly(alkylidenebisaryloxyalkyl-co-alkylene terephthalate) are described. The described elements can be sensitized and charged either negatively or positively and used to prepare images electrophotographically.

Miited States Patent Inventor Stewart H. Merrill Rochester, N.Y.

Appl. No. 772,362

Filed Oct. 31, 1968 Patented Oct. 26, 1971 Assignee Eastman KodakCompany Rochester, NY.

PHOTUCONDUCTIWE ELEMENTS CONTAINHNG POLYMERIC BKNDIERS 17 Claims, NoDrawings 11.8. C1 96/15, 260/47 C 1m. (31 603g 5/00, C08g19/O0, HOlc13/00 Field of Search 260/47 C;

[56] References Cited UNITED STATES PATENTS 3,245,786 4/1966 Cassiers etal. 96/1 3,408,182 10/1968 Mammino 96/15 OTHER REFERENCES 794,773Defense Publication 260/47 (C) 863 O.G. 1001 Primary Examiner-George F.Lesmes Assistant ExaminerM. B. Wittenberg Attorneys-William H. J. Kline,James R. Frederick and Fred L. Denson PHOTOCONDUCTIVE ELEMENTSCONTAINING POLYMERIC lBllNDERS This invention relates to novelelectrophotographic elements having coatings of binder-containingphotoconductive compositions.

Binder-containing photoconductive compositions have been widely used inthe preparation of electrophotographic elements. in electrophotographicreproduction processes, these elements are utilized in the formation oflatent electrostatic images. In some applications the photoconductivecompositions contain an organic photoconductor and a sensitizeruniformly admixed in an inert resinous binder. Many binders arecurrently used in connection with a wide variety of available organicphotoconductor compounds and compositions. Typical binders are ordinarypolymeric materials, e.g., phenolic resins, ketone resins, acrylic esterresins, polystyrene, etc. However, these binders usually do not impartany particular improvement in light sensitivity to the system. The lightsensitivity as indicated by the electrical speed of these particularsystems is ordinarily due wholly to the organic photoconductor andsensitizer. Other binders have been found to contribute significantly tothe light sensitivity of the system. However, the selection of thesepolymers for incorporation into photoconductive compositions to formelectrophotographic layers has proceeded on a compound-by-compoundbasis. Nothing has yet been discovered from the numerous binders testedwhich permits effective prediction and selection of particular polymersexhibiting the desired properties.

it is, therefore, an object of this invention to provide improved novelbinder-containing photoconductive compositions which exhibit high lightsensitivities.

It is another object to provide transparent electrophotographic elementshaving the high speed characteristic of the novel photoconductivecompositions of this invention.

These and other objects of this invention are accomplished by aphotoconductive composition which contains a photoconductor by aphotoconductive composition which contains a photoconductor admixed witha binder therefor which is a poly(alkylidenebisaryloxyalkyl-co-alkyleneterephthalate) wherein the alkylene moiety contains three to l carbonatoms. It has been discovered that such compositions exhibit increasedlight sensitivities as evidenced by greater speeds. In particular,substantial increases in speeds are obtained as compared to speedsattainable with many other polymeric binder compositions. Theseincreases in speed are observed when the coating accepts a suitablepotential (e.g., 500-600 volts) and the relative speed of the coating isdetermined on the basis of the reciprocal of the exposure required toreduce the potential of the surface charge by 100 volts (shoulder speed)or to 100 volts (toe speed). The reduction of the surface potential to100 volts or below is significant in that it represents a requirementfor suitable broad area development ofa latent image. The relative speedat 100 volts in a measure of the ability to produce and henceforth todevelop or otherwise utilize the latent image. When the photoconductoris absent from the coating and only a conventional binder is used, thesurface potential does not drop to or below 100 volts and therefore nospeed can be assigned to such a composition. When a photoconductor ispart of the coating in many conventional polymeric binders, the surfacepotentials of such resultant compositions usually drop below 100 volts,and thus, a definitespeed can be ascertained. How ever, these speeds areimproved when the binders of this invention are employed.

The poly(alkylidenebisaryloxyalkyl-co-alkylene terephthalate)copolyesters of this invention include those consisting essentiallyofthe following repeating units:

wherein Z is an alkylene group having three to 10 carbon atoms includingsubstituted as well as unsubstituted alkylene radicals such as a. astraight chain or branched alkylene hydrocarbon radical, e.g., thoserepresented by the formula R1 -c 6 m l l i I R2 where R,, R R and R areeither hydrogen or an alkyl radical having one to five carbon atoms, sis an integer from zero to seven when R or R is an alkyl radical and oneto seven when R and R are hydrogen and I is an integer from one toseven, including a trimethylene radical, a tetramethylene radical, apropylene radical, a pentamethylene radical a neopentylene radical, ahexamethylene radical, etc;

b. an oxydialkylene radical or a thiadialkylene radical, e.g., thoserepresented by the formula where D is an oxygen or sulfur atom and n and0 are integers from two to seven including an oxydiethylene radical, athiadiethylene radical, etc.;

c. an alkylene bis(oxyalkylene) radical or an alkylene bis(thiaalkylene)radical, e.g., those represented by the forwhere D is an oxygen orsulfur atom and p, q and r are integers from two to six, including amethylene bis(oxyethylene) radical, an ethylene bis(thiaethylene)radical, an ethylene bis(oxyethylene radical), etc.

d. a cycloalkylene hydrocarbon radical including substitutedcycloalkylene hydrocarbon radicals, e.g., those represented by theformula where Q is the atoms necessary to complete a 3 to 6 carboncycloalkylene radical and u and v are integers from zero to five,including a cyclohexylenediemthylene radical, acyclopentylenedimethylene radical, a cyclobutylenediemthylene radical, acyclobutylenediethylene radical, a cyclobutylene radical,2,2,4,4-tetramethyl-l,3-cyclobutylene radical, etc;

e. D and E each can be a hydrogen atom, a halogen atom, an

alkyl group, an aryl group, an alkoxy group or an aryloxy group. Thecopolyester binders of this invention suitably contain 2 to percent andpreferably 30 to 60 percent of repeating unit A. The binder alsosuitably contains from about 20 to 98 percent and preferably 40 to 70percent of repeating unit B. The polymer contains these units arrangedin a random, linear fashion. Binders comprising such polymers improvethe electrical speed of the photoconductive composition.

Exemplary of a few of the many polymers useful as binders in thisinvention are:

l. Poly(4,4'-isopropylidenebisphenoxyethyl-co-trimethylene 3.Poly(4,4-isopropylidenebisphenoxyethyl-co-pentamethylene terephthalate)4. Poly(4,4'-isopropylidenebisphenoxyethyl-co-oxydiethyleneterephthalate) 5. Poly(4,4-isopropylidenebisphenoxyethyl-co-neopentylterephthalate) phthalate) 6.Poly(4,4-isopropylidenebisphenoxyethyl-co-cyclohexylenedimethyleneterephthalate) 7.Poly(4,4-isopropylidenebisphenoxyethyl-co-cyclobutylenedimethyleneterephthalate) 8.Poly(4,4'-isopropylidenebisphenoxyethyl-co-thiadiethylene terephthalate)9. Poly[4,4-isopropylidenebisphenoxyethyl-co-ethylenebis(oxyethylene)terephthalate] l0.Poly[4,4-isopropylidenebisphenoxyethyl-co-ethylenebis(thiaethylene)terephthalate] l l. Poly(4,4'-isopropylidenebisphenoxyethyl-co-2,2,4,4-tetramethyl-l ,3-cyclobutylene terephthalate) 12. Poly(4,4-isopropylidenebisphenoxyethyl-cotetramethylene-4-bromoterephthalate)13.Poly(4,4'-isopropylidenebisphenoxyethyl-cotetramethylene-S-phenoxyterephthalate)14. Poly( 4,4-isopropylidenebisphenoxyethyl-co-propylene terephthalate)l5 Poly(4,4-isoprpylidenebisphenoxyethyl-cotetramethylene-2,S-dichloroterephthalate)16. Poly(4,4-isopropylidenebisphenoxyethyl-cotetramethylene--methoxyterephthalate)17. Poly(4,4'-isopropylidenebisphenoxyethyl-cotetramethylene-S-phenylterephthalate)In preparing typical electrophotographic elements utilizing thepolymeric binders of this invention, an organic photoconductor isdissolved in a solution of binder and solvent and then, after thoroughmixing, the composition is coated on an electrically conducting supportin a well-known manner, such as swirling, spraying, doctor bladecoating, and the like.

The novel binders of this invention improve the electrical speeds ofcompositions containing a wide variety of photoconductors includinginorganic photoconductors such as zinc oxide, titanium dioxide, cadmiumsulfide and the like and organic photoconductors includingorganometallic photoconductors.

Typical photoconductors useful with the binders of this inventions aredescribed below.

B. Photoconductors represented by the formula wherein A represents anononuclear or polynuclear divalent aromatic radical, either fused orlinear (cg, phenyl, naphthyl, biphenyl, binaphthyl, etc.), or asubstituted divalent aromatic radical of these types wherein saidsubstitutent can comprise a member such as an acyl group having from oneto about six carbon atoms (e.g., acetyl, propionyl, butryl, etc.), analkyl group having from one to about six carbon atoms (e.g., methyl,ethyl, propyl, butyl, etc.), an alkoxy group having from one to aboutsix carbon atoms (e.g., methoxy, ethoxy, propoxy, pentoxy, etc), or anitro group; A represents a mononuclear or polynuclear monovalentaromatic radical, either fused or linear (e.g., phenyl, naphthyl,biphenyl, etc), or a substituted monovalent aromatic radical whereinsaid substituent can comprise a member, such as an acyl group havingfrom one to about six carbon atoms (e.g., acetyl,

propionyl, butyryl, etc), an alkyl group having from one to about sixcarbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy grouphaving from one to about six carbon atoms (e.g., methoxy, propoxy,pentoxy, etc.), or a nitro group; O can represent a hydrogen atom or anaromatic amino group, such as A'NH-; b represents an integer from one toabout twelve, and L represents a hydrogen atom, a mononuclear orpolynuclear aromatic radical, either fused or linear (e.g., phenyl,naphthyl, biphenyl, etc.), a substituted aromatic radical wherein saidsubstituent comprises an alkyl group, alkoxy group, an acyl group, or anitrate group or a poly(4'-vinylphenyl) group which is bonded to thenitrogen atom by a carbon atom of the phenyl group, these materialsbeing more fully described in U.S. Pat. No. 3,265,496.

C. Polyarylalkane photoconductors including leuco bases of diaryl ortriarylmethane dye salts, l,l l-triarylakanes wherein the alkane moietyhas at least two carbon atoms and tetraaryl methanes having an aminogroup substituted in at least one of the aryl nuclei attached to thealkane and methane moeties of the latter two classes of photoconductorswhich are nonleuco base materials; and also other polyarylalkanesincluded by the formula HLE wherein each of D, E and G is an aryl groupand J is a hydrogen atom, an alkyl group, or an aryl group, at least oneof D, E and G containing an amino substituent, the aryl groups attachedto the central carbon atom being preferably phenyl groups, althoughnaphthyl groups can also be used including substituted aryl groupscontaining substituents such as alkyl and alkoxy typically having one toeight carbon atoms, hydroxy, halogen, etc. in the ortho, meta or parapositions, ortho-substituted phenyl being preferred; the aryl groups canalso be joined together or cyclized to form a fluorene moiety, forexample; the amino substituent can be represented by the formula whereineach R can be an alkyl group typically having one to eight carbon atoms,a hydrogen atom, an aryl group, or together the necessary atoms to forma heterocyclic amino group typically having five to six atoms in thering such as morpholino, pyridyl, pyrryl, etc.', at least one of D, Eand G preferably being a p-dialkylaminophenyl groups, when J is an alkylgroup, such an alkyl group more generally has one to seven carbon atoms,these materials being more fully described in U.S. pat. No. 3,274,000,French Pat. No. l,383,46l and in U.S. Ser. No. 627,857 filed Apr. 3,1967 by Seus and Goldman, now U.S. Pat. No. 3,542,544.

D. Photoconductors comprising 4-diarylamino-substituted chalcones havingthe formula wherein R and R, are each aryl radicals, aliphatic residuesof one to 12 carbon atoms such as alkyl radicals preferably having oneto four carbon atoms, or hydrogen; particularly advantageous resultsbeing obtained when R is a phenyl radical including a substituted phenylradical and where R is diphenylaminophenyl, di-methylaminophenyl orphenyl, these materials being more fully described in Fox application,U.S. Ser, No. 613,846, now U.S. Pat. No. 3,526,50l.

E. Nonionic cycloheptenyl compounds which may be substituted withsubstituents such as (a) an aryl radical including substituted as wellas unsubstituted aryl radicals, (b) a hydroxy radical, (c) an azidoradical, (d) a heterocyclic radical having five to six atoms in theheterocyclic nucleus and at least one heteronitrogen atom, and includingsubstituted and unsubstituted heterocyclic radicals, and (e) anoxygen-linked cycloheptenyl moiety. The substitution on thecycloheptenyl nucleus occurs at an unsaturated carbon atom when thecycloheptenyl moiety is a conjugated triene with no aromatic structurefused thereto. However, if there is at least one arematic structurefused to the cycloheptenyl moiety, then the substituents are attached toa saturated carbon atom. Additional photoconductors within this classare included in one of the following formulas where E and G can beeither:

a. a phenyl radical,

b. a naphthyl radical,

c. a heterocyclic radical having five to six atoms in the heterocyclicnucleus and at least one heteronitrogen atom,

d. a hydroxyl radical, or

e. an oxygen-containing radical having a structure such that theresultant cycloheptenyl compound is a symmetrical ether; nucleus anddnucleus; 11967, D can be any of the substituents defined for E and Gabove and is attached to a carbon atom in the cycloheptenyl nucleushaving a double bond; (R and R,,,), (R and R (R,, and R and (R, and Rare together the necessary atoms to complete a benzene ring fused to thecycloheptenyl nucleus; these compounds being more fully described inU.S. Ser. No. 654,091 filed July 18, 1967, now U.S. Pat. No. 3,533,786.

F. Compounds containing an as a haloalkyl or an alkoxyalkyl radical,

b. a phenyl radical including a substituted phenyl radical such as anaphthyl, an aminophenyl or a hydroxyphenyl radical,

c. a halogen atom,

d. an amino radical including substituted as well as unsubstituted aminoradicals such as an alkylamino or a phenyl-alkylamino radical;

e. an alkoxy radical,

f. a hydroxyl radical,

g. a cyano radical,

h. a heterocyclic radical such as a pyrazyl, a carbazolyl or a pyridylradical; or (2) tetra-substituted hydrazines containing substituentswhich are substituted or unsubstituted phenyl radicals, or heterocyclicradicals having five to six atoms in the heteronucleus, suitable resultsbeing obtained when all four substituents are not unsubstituted phenylradicals, i.e., if at least on substituent is a substituted phenylradical or a heterocyclic radical having five to six atoms in theheteronucleus. Other tetra-substituted hydrazines include those havingthe following formula:

wherein D,, E G, and J are each either a. a substituted phenyl radicalsuch as a naphthyl radical, an alltylphenyl radical, a halophenylradical, a hydroxyphenyl radical, a haloalkylphenyl radical or ahydroxyalkylphenyl radical or b. a heterocyclic radical such as animidazolyl radical, a furyl radical or a pyrazoline radical.

In addition, J l and E 1 can also be c. an unsubstituted phenyl radical,Especially preferred are those tetra-substituted hydrazines wherein bothD, and G are either substituted phenyl radicals or heterocyclicradicals. These compounds are more fully described in U.S. Ser. No.673,962 filed Oct. 9, 1967, now U.S. Pat. No. 3,542,546.

G. Organic compounds having a 3,3'-bis-aryl-2-pyrazoline nucleus whichis substituted in either five-member ring with the same or differentsubstituents. The one and five positions on both pyrazoline rings can besubstituted by an aryl moiety including unsubstituted as well assubstituted aryl substituents such as alkoxyaryl, allcaryl,alkaminoaryl, carboxyaryl, hydroxyaryl and haloaryl. The four positioncan contain hydrogen or unsubstituted as well as substituted alltyl andaryl radicals such as alltoxyaryl, alkaryl, alkaminoaryl, haloaryl,hydroxyaryl, alkoxyallcyl, aminoalkyl, carboxyaryl, hydroxyalkyl andhaloalkyl. Other photoconductors in this class are represented by thefollowing structure:

D D';,, 1;, and J' can be either a phenyl radical including asubstituted phenyl radical such as a tolyl radical or a naphthyl radicalincluding a substituted naphthyl radical,

E E' G G' L and L';, can be any of the substituents set forth above andin addition can be either a hydrogen atom or an alkyl radical containingone to eight carbon atoms. These organic photoconductors are more fullydescribed in U.S. Ser. No. 664,642 filed Aug. 31, 1967., now U.S. Pat.No. 3,527,602.

1H. Triarylamines in which at least one of the aryl radicals issubstituted by either a vinyl radical or a vinylene radical having atleast one active hydrogen-containing group. The phrase vinylene radical"includes substituted as well as unsubstituted vinylene radicals and alsoincludes those radicals having at least one and as many as threerepeating units of vinylene groups such as (Ch =CH) wherein n is aninteger of from one to three. Groups which contain active hydrogen arewell known in the art, the definition of this term being set forth inseveral textbooks such as Advanced Organic Chemistry," R. C. Fuson, pp.154-157, John Wiley & Sons, 1950. The term active hydrogen'containinggroup" as used herein includes those compounds encompassed by thediscussion in the textbook cited above and in addition includes thosecompounds which contain groups which are hydrolyzable to activehydrogen-containing groups. Typical active hydrogen-containing groupssubstituted on the vinyllene radical of the triarylamine include:

a. carboxy radicals,

b. hydroxy radicals,

c. ethynyl radicals,

d. ester radicals (e.g.,

wherein R is alkyl or aryl) including cyclic ester radicals wherein R isa cyclic alkylene radical connected to a vinylene combination such as isfound in coumarin derivatives),

e. carboxylic acid anhydride radicals,

f. semicarbazano radicals,

g. cyano radicals,

h. acyl halide radicals (e.g.,

etc.), and

i. amido radicals (e.g.,

wherein R is a hydrogen atom, an alkyl group or an aryl group).

Other active hydrogen-containing groups include substituted andunsubstituted alkylidyne oximido radicals. Photoconductors included inthis class can be represented by the following structure:

wherein:

a. Ar and Ar are each a phenyl radical including a substituted phenylradical such as a halophenyl radical, an alkyl phenyl radical or anaminophenyl radical;

b. Ar, is an arylene radical including a substituted arylene radicalsuch as a phenylene radical or a naphthylene radical;

c. R and R are each hydrogen, a phenyl radical including a substitutedphenyl radical or a lower alkyl radical preferably having one to eightcarbon atoms;

d. X is either (1) an active hydrogen-containing group such as a carboxyradical, an acyl halide radical, an amido radical, a carboxylic acidanhydride radical, an ester radical, a cyano radical, a hydroxy radical,a semicarbazono radical, an ethynyl radical, or a methylidyne oximidoradical, or (2) hydrogen, provided that when X is hydrogen R and R arealso hydrogen: and

e. n is an integer ofone to three.

The arylene nucleus can be substituted in any position by the vinyl orvinylene moiety. However, when Ar is phenylene, particularly goodresults are obtained if the substitution occurs in the para position.These material are more fully described in US. Ser. No. 706,800 filedFeb. 20, 1968, now US. Pat. No. 3,567,450.

I. Triarylamines in which at least one of the aryl radicals issubstituted by an active hydrogen-containing groups. The term activehydrogen-containing group" has the same meaning as set forth above andagain includes those compounds encompassed by the discussion in thetextbook and additionally includes those compounds which contain groupswhich are hydrolyzable to active hydrogen-containing groups. Typicalactive hydrogen-containing groups which are substituted on an arylradical of the triarylamine include:

a. carboxy radicals;

b. hydroxy radicals;

c. ethynyl radicals;

d. ester radicals (e.g.,

0 iii??? where in R is an alkyl or an aryl group);

e. lower alkylene hydroxyl radicals (e.g., having one to eight carbonatoms);

f. carboxylic acid anhydride radicals;

g. lower alkylene carboxy radicals (e.g., having two to eight carbonatoms);

h. cyano radicals;

i. acyl halide radicals e.g.,

etc.);

j. amido radicals (e.g.,

O in a N wherein R is a hydrogen atom, an alkyl group or an aryl group);

k. lower alkylidyne oximido radicals having one to eight carbon atomsincluding substituted alkylidyne oximido radicals (e.g.,

wherein R is hydrogen or a lower alkyl radical);

l. semicarbazono radicals; and

m. arylene carboxy radicals including substituted arylene carboxyradicals (e.g.,

wherein D, and are phenyl or lower alkyl radicals. Photoconductorsincluded in this class can be represented by the following structure:

wherein:

a. Ar, and Ar, are each a phenyl radical including a substituted phenylradical such as a halophenyl radical, an alkyl phenyl radical or anamino phenyl radical;

b. Ar is an arylene radical including a substituted arylene radical suchas a phenylene radical or a naphthylene radical; and

c. X is an active hydrogen-containing group such as a carboxy radical,an acyl halide radical, an amido radical, a carboxylic acid anhydrideradical, an ester radical, a cyano radical, a semicarbazono radical, ahydroxy radical. an ethynyl radical, a methylidyne oximido radical or aphenylene carboxy radical. These material are more fully described inUS. Ser. No. 706,780 filed Feb. 20, 1968.

J. Organometallic compounds having at least one aminoaryl substituentattached to a Group We or Group Va metal atom. The metallic substituentsof this class of organic photoconductors are Group lVa or Group Vametals in accordance with the Periodic Table of the Elements (Handbookof Chemistry and Physics, 38th edition, pp. 394-) and include silicon,germanium, tin and lead from Group lVaand phosphorus, arsenic, antimonyand bismuth from Group Va. These materials can be substituted in themetallo nucleus with a wide variety of substituents but at least one ofthe substituents must be an amino-aryl radical. The amino radical can bepositioned anywhere on the aromatic nucleus. but best results areobtained if the aryl moiety is a phenyl radical having the amino groupin the four or para position. Typical substituents attached to the metalnucleus include the following:

a. a hydrogen, sulfur or oxygen atom,

b. an alkyl radical,

c. an aryl radical including unsubstituted as well as substituted arylradicals such as aminoaryl, alkylaryl and haloaryl,

d. an oxygen-containing radical such as an alkoxy or aryloxy radical,

e. an amino radical including unsubstituted and substituted aminoradicals such as monoand diarylamino and monoand dialkylamino radicals,

f. a heterocyclic radical and g. a Group [Va or Va organometallicradical. Photoconductors included in this class can be represented bythe following structures:

where E G L and Q can be a. a hydrogen atom,

b. an aryl radical including unsubstituted as well as substituted arylradicals such as a phenyl radical, a naphthyl radical, adialkylaminophenyl radical, or a diarylaminophenyl radical,

c. an alkyl radical having one to eight carbon atoms,

d. an alkoxy radical having one to eight carbon atoms,

e. an aryloxy radical such as a phenoxy radical,

f, an amino radical having the formula wherein R and R can be hydrogenatoms or alkyl radicals having one to eight carbon atoms, or

g. a heterocyclic radical having five to six atoms in the hetero nucleusincluding at least one nitrogen atom such as a triazolyl, a pyridylradical, etc.; T is an amino radical such as an alkylarnino radicalhaving one to eight carbon atoms or an arylamino radical such as aphenylamino radical; Ar is an aromatic radical such as phenyl ornaphthyl;

M and M"2 are the same or different Group lVa metals;

M,, is a Group Va metal;

D, can be any of the substituents set forth above for E G L and Q and inaddition can be a Group lVa orzanometallic radical or when taken with E,

atom or a sulfur atom. These materials are described in US. Ser. No.650,664 filed July 3, 1967.

K. Any other organic compound which exhibits photoconductive propertiessuch as those set forth in Australian Pat. No. 248,402.

Representative organic photoconductors useful in this invention includethe compounds listed below:

TABLE I diphenylamine dinaphthylamine N,N'-diphenylbenzidineN-phenyl-l-naphthylmaine N-phenyl-Z-naphthylamineN,N-diphenyl-p-phenylenediamine2-carboxy-5-chloro-4'-methoxydiphenylamine p-anilinophenolN,N'-di-2-naphthyl-p-phenylenediamine 4,4-benzylidene-bis-(N,N-dimethyl-m-toluidine) triphenylamineN,N,N',N'-tetraphenyl-m-phenylenedia:mine 4-acetyltriphenylamine4-hexanoyltriphenylamine 4-lauroyltriphenylamine 4-hexyltriphenylamine4-dodecyltriphcnylamine 4, 4'-bis(diphenylamino)benzil 4,4'-bis(diphenylamino)benzophenone polylN,4"-(N,N,N'-triphenylbenzidine)]polyadipyltriphenylamine polysebacyltriphenylaminepolydecamethylentriphenylaimne plly-N-O 4-vinylphenyl)diphenylaminepoly-N-(vinylphenyl)-a,a'-dinaphthylamine 4,4-benzylidine-bis(N,N,-diethyl-m-toluidine)4',4"-diamino4-dimethylamino-Z,2"-dimethyltriphenylmethane 4,"4"-bis(diethylamino)-2, 6-dichloro-2 2"-dimethyltriphenylmethane4',4"-bis(diethylamino)-2,2"-dimethyldiphenylnaphthylmethane2',2"-dimethyl-4,4',4"-tris(dimethylamino)triphenylmethane 4',4' '-bis(diethylamino )-4-dimethylamino-2 ,2 "-dimethyltriphenylmethane 4' ,4-bis( diethylamino )-2-chloro-2 ,2 "-dimethyl-4-dimethylaminotriphenylmethane 4',4 '-bis(diethylamino)-4-dimethylamino-2 ,2 ,2 '-trimethyltriphenylmethane4',4"-bis(dimethylmaino )-2-chloro-2 ',2 '-dimethyltriphenylmethane4',4"-bis( dimethylamino )-2 ,2 -dimethyl-4methoxytriphenylmethaneBis(4-diethylamino l l l -triphenylethane Bis( 4 diethylamino)tetraphenylmethane:

4 ,4 "bis( benzylethylamino )-2',2' -dimethyltriphenylmethane 4',4'-bis( diethylmaino )-2,2 '-diethoxytriphenylmethane4,4-bis(dimethylamino)-l ,l l -triphenylethanel-(4-N,N-dimethylaminophenyl)-l l -diphenylethane4-dimethylaminotetraphenymethane 4-diethylaminotetraphenylmethane4,4'-bis (diphenylamino) chalcone4-diphenylamino-4'-dimethylaminochalcone4-dimethylamino-4'-diphenylaminochalcone 4,4-bis (dimethylamino)chalcone 4,4'-bis (diethylamino) chalcone 4-diethylamine4-diphenylaminochalcone 4,4 (n-amyloxy) chalcone 4,4'-bis( nitro)chalcone 4-diphenylaminochalcone 4-dimethylaminochalconediazabenzo(b)fluorene, 3,l3-dioxo- 7-oxadibenzo(b,g)fluorene, and thelike; aromatic nitro compounds of the kinds described in U.S. Pat. No.2,610,120; anthrones like those disclosed in U.S. Pat. No. 2,670,284;quinones, U.S. Pat. No. 2,670,286; benzophenones U.S. Pat. No.2,670,287; thiazoles U.S. Pat. No. 2,732,301; mineral acids; carboxylicacids, such as maleic acid, dichloroacetic acid, and salicyclic acid;sulfonic and phosphoric acids; and various dyes, such as cyanine(including carbocyanine), mercoycanine, diarylmethane, thiazine, azine,oxazine, xanthene, phthalein, acridine, azo, anthraquinone dyes and thelike and mixtures thereof. The sensitizers preferred for use with thecompounds of this invention are selected from pyrylium includingselenapyrylium and thiapyrylium salts, and cyanine includingcarbocyanine dyes.

Where a sensitizing compound is employed with the binder and organicphotoconductor to form a sensitized electrophotographic element, it isthe normal practice to mix a suitable amount of the sensitizing compoundwith the coating composition so that, after thorough mixing, thesensitizing compound is uniformly distributed in the coated element.Other methods of incorporating the sensitizer of the effect of thesensitizer may, however, be employed consistent with the practice ofthis invention. In preparing the photoconductive layers, no sensitizingcompound is required to give photoconductivity in the layers whichcontain the photoconducting substances, therefore, no sensitizer isrequired in a particular photoconductive layer. However, sincerelatively minor amounts of sensitizing compound give substantialimprovement in speed in such layers, the sensitizer is preferred. Theamount of sensitizer that can be added to a photoconductorincorporatinglayer to give effective increases in speed can vary widely. The optimumconcentration in any give case will vary with the specificphotoconductor and sensitizing compound used. In general, substantialspeed gains can be ob tained where an appropriate sensitizer is added ina concentration range from about 0.0001 to about 30 percent by weightbased on the weight of the film-forming coating composition. Normally, asensitizer is added to the coating composition in an amount by weightfrom about 0.005 to about 5.0 percent by weight of the total coatingcomposition.

Solvents useful for preparing coating compositions with the binders ofthe present invention can include a wide variety of organic solvents forthe components of the coating composition. For example, benzene;toluene; acetone; Z-butanone; chlorinated hydrocarbons such as methylenechloride; ethylene chloride; and the like; ethers, such astetrahydrofuran and the like, or mixtures of such solvents canadvantageously be employed in the practice of this invention.

In preparing the coating compositions utilizing the binders disclosedherein useful results are obtained where the photoconductive substanceis present in an amount equal to at least about 1 weight percent of thecoating composition. The upper limit in the amount ofphotoconductivematerial present can be widely varied in accordance with usual practice.It is normally required that the photoconductive material be present inan amount ranging from about 1 Weight percent of the coating compositionto about 99 weight percent of the coating composition. A preferredweight range for the photoconductive material in the coating compositionis from about 10 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support canvary widely. Normally, a wet coating thickness in the range of about0.001 inch to about 0.01 inch is useful in the practice of theinvention. A preferred range of coating thickness is from about 0.002inch to about 0.006 inch before drying although such thicknesses canvary widely depending on the particular application desired for theelectrophotographic element.

Suitable supporting materials for coating the photoconductive layersofthe present invention can include any of the electrically conductingsupports, for example, paper (at a relative humidity above percent);aluminum-paper laminates; mptal fnile cnr'h as aluminum foil. zinc foil.etc.: metal plates.

such as aluminum, copper, zinc, brass, and galvanized plates; vapordeposited metal layers such as silver, nickel or aluminum orconventional film supports such as cellulose acetate, poly(ethyleneterephthalate), polystyrene and the like conducting supports.

An especially useful conducting support can be prepared by coating afilm support material such as poly(ethylene terephathalate) with a layercontaining a semiconductor dispersed in a resin. A suitable conductingcoating can be prepared from the sodium salt of a. carboxyester lactoneof maleic anhydride and a vinyl acetate: polymer, cuprous iodide and thelike. Such conducting layers and methods for their optimum preparationand use are disclosed in U.S. Pat. Nos. 3,007,901, 3,245,833 and3,267,807.

The compositions of the present invention can be employed inphotoconductive elements useful in any of the well-knownelectrophotographic processes which require photoconduo tive layers. Onesuch process is the xerographic process. In a process of this type, anelectrophotographic element held in the dark is given a blanketelectrostatic charge by placing it under a corona discharge to give auniform charge to the surface of the photoconductive layer. This chargeis retained by the layer'owing to the substantial dark insulatingproperty of the layer, i.e., the low conductivity of the layer in thedark. The electrostatic charge formed on the surface of thephotoconductive layer is then selectively dissipated from the surface ofthe layer by imagewise exposure to light by means of a conventionalexposure operation such as for example, by a contact-printing technique,or by lens projection of an image, or reflex or bireflex techniques andthe like, to thereby form a latent electrostatic image in thephotoconductive layer. Exposing the surface in this manner forms apattern of electrostatic charge by virtue of the fact that light energystriking the photoconductor causes the electrostatic charge in thelightstruck areas to be conducted away from the surface in proportion tothe intensity ofthe illumination. in a particular area.

The charge pattern produced by exposure is then developed or transferredto another surface and developed there, i.e., either the charge oruncharged areas rendered visible, by treatment with a medium comprisingelectrostatically responsive particles having optical density. Thedeveloping electrostatically responsive particles can be in the form ofa dust or powder and generally comprise a pigment in a resinous carriercalled a toner. A preferred method of applying such a toner to a latentelectrostatic image for solid area development is by the use of amagnetic brush. Methods of forming and using a magnetic brush tonerapplicator are described in thefollowing U.S. Pats: Nos. 2,786,439;2,786,440.; 2,786,441; 2,811,465; 2,874,063; 2,984,163; 3,040,704;3,117,884; and reissue Re 25,779. Liquid development of the latentelectrostatic image may also be used. In liquid development thedeveloping particles are carried to the image-bearing surface in anelectrically insulating liquid carrier. Methods of development of thistype are widely known and have been described in the patent literature,for example, US. Pat. No. 2,297,691 and in Australian Pat. No.212,315.1n dry developing processes the most widely used method ofobtaining a permanent record is achieved by selecting a developingparticle which has as one of its components a low-melting resin. Heatingthe powder image then causes the resin to melt or fuse into or on theelement. The powder is, therefore, caused to adhere permanently to thesurface of the photoconductive layer In other cases, a transfer of thecharge image or powder image formed on the photoconductive layer can bemade to a second support such as paper which would then become the finalprint after developing and fusing or fusing respectively. Techniques ofthe type indicated are well known in the art and have been described ina number of U.S. and foreign patents, such as U.S. Pats. Nos. 2,297,691and 2,551,582, and in RCA Review, vol. 15 (1954) pages 469-484 Thecompositions of the present invention can be used in electrophotographicelements having many structural variations. For example. thephotoconductive composition can be coated in the form of single layersor multiple layers on a suitable opaque or transparent conductingsupport. Likewise, the layers can be contiguous or spaced having layersof insulating material or other photoconductive material between layersor overcoated or interposed between the photoconductive layer orsensitizing layer and the conducting layer. It is also possible toadjust the position of the support and the conducting layer placing aphotoconductor layer over a support and coating the exposed face of thesupport or the exposed or overcoated face of the photoconductor with aconducting layer. Configurations differing from those contained in theexamples can be useful or even preferred for the same or differentapplication for the electrophotographic element.

The following examples are included for a further understanding of thisinvention.

EXAMPLE l 1.5 grams of 4,4-isopropylidenebisphenoxyethyl-cotrimetyleneterephthalate) binder containing 0.5 grams of4,4'-benzylidine-bis(N,N-diethyl-m-toluidine) photoconductor and .04grams of 2,4-(4-ethoxypheny1)-6(4-n-amlyoxystryl) pyrylium fluoroboratesensitizer are dissolved in 15.6 grams of methylene chloride by stirringthe solids in the solvent for one hour at room temperature. Theresulting solution is hand coated at a wet coating thickness of 0.004inch on a conducting layer comprising the sodium salt of a carboxyesterlactone, such as described in U.S. Pat. No. 3,120,028, which in turn iscoated on a cellulose acetate film base. The coating block is maintainedat a temperature of 90 F. After drying, the electrophotographic elementis charged under positive corona source until the surface potential, asmeasured by an electrometer probe, reaches about 600 volts. It is thensubjected to exposure from behind a stepped density gray scale to a 3000K. tungsten source. The exposure causes reduction of the surfacepotential of the element under each step of the gray scale from itsinitial potential, V,, to some lower potential, V, whose exact valuedepends on the actual amount of exposure in meter-candle-secondsreceived by the area. The results of the measurements are plotted on agraph of surface potential V vs. log exposure for each step. Theshoulder speed is the numerical expression of multiplied by thereciprocal of the exposure in meter-candle-seconds required to reducethe 600 volt charged surface potential by 100 volts. The toe speed isthe numerical expression of IO multiplied by the reciprocal of theexposure in meter-candle-seconds required to reduce the 600 volt chargedsurface potential to 100 volts. This coating is found to have a positive100 V. toe speed of 180. Similar results are obtained when 0.5 gram ofbis(4- diethylamino)-l, l,l-triphenylethane or 0.5 gram of bis(4-diethylamino)tetraphenylmethane are used as photoconductors in place ofthe 4,4 -benzylidine bis(N,N-diethyl mtoluidine) for both positive andnegative charging. 30

EXAMPLE 2 Example 1 is repeated except the binder employed ispoly(4,4-isopropylidenebisphenoxyethyl-co-ethylene terephthalate). Thisbinder does not fall within the scope of the invention since thealkylene moiety (i.e., 2) has only two carbon atoms and is included forcomparison purposes only. The coating has a positive l00-volt toe speedof 128.

The following examples 3-5 are identical to example 1 except for thebinder employed. 1.5 grams of various binders are used in each of thefollowing examples. In each case a significant improvement is noted inthe l00-volt toe speeds over binders of the type described in thepreceding example.

EXAMPLE 6 The coating compositions of Examples 1 and 3-5 are againcoated in the manner described in example 1. In a darkened room, thesurface of each of the photoconductive layers so prepared is charged toa potential of about +600 volts under a corona charger. The layer isthen covered with a transparent sheet bearing a pattern of opaque andlight-transmitting areas and exposed to the radiation from anincandescent lamp with an illumination intensity of about 75meter-candles for 12 seconds. The resulting electrostatic latent imagelS developed in the usual manner by cascading over the surface of thelayer a mixture of negatively charged black thermoplastic tonerparticles and glass beads. A good reproduction of the pattern results ineach instance EXAMPLE 7 The copolyesters described herein are made bystandard melt condensation techniques. Poly(44'-isopropylidenebisphenoxyethyl-co-tetramethylene terephthalate) isprepared by mixing 0.15 moles of dimethyl terephthalate, 0.075 moles of4,4-isopropylidenebisphenoxyethanol, 0.10 moles of tetramethylene glycoland 0.05 grams of tetrabutyl orthotitanate. Nitrogen is bubbled throughthe mixture, and it is heated at 200 C. for 2 hours to distill offmethanol. The temperature is raised to 250 C. and vacuum applied untilcomplete polymerization is completed. The resultant polymer contains 50percent of repeating unit A and 50 percent B. The other polymers areprepared by the same method by replacing tetramethylene glycol with theappropriate compound. For example, trimethylene glycol would be used toprepare polymer 1, pentamethylene glycol for polymer 3, diethyleneglycol for compound 4, etc.

The invention has been described in detail with particular reference topreferred embodiments thereof but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

lclaim:

1. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising a photoconductor and abinder for said photoconductor comprising a polyester having repeatingunits of wherein Z is an alkylene group having three to ten carbonatoms, and D and E are each selected from the group consisting of ahydrogen atom, a halogen atom, an aryl group, an alkyl group, an aryloxygroup and an alkoxy group.

2. The electrophotographic element of claim 1 wherein Z is selected fromthe group consisting of a. a straight chain alkylene hydrocarbonradical,

b. an oxydialkylene radical,

c. an alkylene bis(oxyalkylene) radical,

d. a cycloalkylene hydrocarbon radical,

e. a branched chain alkylene hydrocarbon radical,

f. a thiadialkylene radical and g. an alkylene bis(thiaalkylene)radical.

3. The electrophotographic element of claim 1 wherein thephotoconductive composition contains a sensitizer selected from thegroup consisting of cyanine and pyrylium dye salts.

d. An electrophotographic element comprising a support having coatedthereon a photoconductive composition com prising an organicphotoconductor, a sensitizer and a binder for said photoconductor andsensitizer, comprising a random, linear copolyester having repeatingunits of and wherein Z is an alkylene group having three to ten carbonatoms, and D and E are each selected from the group consisting of ahydrogen atom, a halogen atom, an aryl group, an alkyl group, an aryloxygroup and an alkoxy group.

5. The electrophotographic element of claim 4 wherein Z is selected fromthe group consisting of t is an integer from one to seven;

n and are each integers from two to seven; u and v are each integersfrom zero to five; p, q and r are each integers from two to six;

s is an integer from one to seven when R and R is hydrogen;

s is an integer from zero to seven when R or R is an alkyl radical;

D is selected from the group consisting of an oxygen atom and a sulfuratom;

Q represents the atoms necessary to complete a three-to-six carbon atomcycloalkyl radical; and

R R R and R are each selected from the group consisting of hydrogen andan alkyl radical having one to five carbon atoms.

6. The electrophotographic element of claim 4 wherein the sensitizer isselected from the group consisting of carbocyanine, pyrylium,thiapyrylium and sel enapyrylium dye salts.

7. The electrophotographic element of claim 4 wherein the organicphotoconductor is 4,4'-benzy'lidenebis(N,N-diethylm-toluidine).

3. The electrophotographic element of claim 4 wherein the binder has 20percent to percent of repeating unit A.

9, The electrophotographic element of claim 4 wherein the binder has 30percent to 60 percent of repeating unit A.

10. The electrophotographic element ofclaim 4 wherein the binder ispoly(4,4'-isopropylidenebisphenoxyethyl-cotrimethylene terephthalate).

11. The electrophotographic element ofclaim 5 wherein the binder ispoly(4,4'-isopropylidenebis-phenoxyethyl-co-tetramethyleneterephthalate).

12. The electrophotographic element ofclaim 5 wherein the binder ispoly(4,4"isopropylidenebisphenoxyethyl-co-pentamethylene terephthalate).

13. The electrophotographic element ofclaim 5 wherein the binder ispoly(4,4'-isopropylidenebisphenoxy-co-oxydiethylterephthalate).

14. An electrophotographic element comprising a support having coatedthereon a photoconductive composition com prising 10 to about 60 weightpercent of 4,4- benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4'-isopropylidenebisphenoxyethyl-co-trimethylene terephthalate)as a binder for said photoconductive composition.

15. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising 10 to about 60 weightpercent of 4,4" benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4'-isopropylidenebisphenoxyethyl-co-tetreamthylene terephthalate)as a binder for said photoconductive composition.

16. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising 10 to about 60 weightpercent of 4,4- benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4-isopropylidenebisphenoxyethyl-co-pentamethylene terephthalate)as a binder for said photoconductive composition.

17. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising 10 to about 60 weightpercent of 4,4- benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4'-isopropylidenebisphenoxyethyl-co-oxydiethyi terephthalate) asa binder for said photoconductive composition.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,6l5,+06 Dated October 26, 197].

Inventor(s) Stewart H. Merrill It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 37, delete "by a photoconductive composition which"; line38, delete "contains a photoconduotor; line 5 4, "in" should read is";lines 67-75, in formula A, the brackets and the letter "E" are notproperly printed.

Column 2, line 20, in formula, "R is not print ed properly in thepatent; line 56 "cyclohexylenediemthylene" should read"cyclohexylenedimethylene"; line 58, tylenediemthylene" should read"tylenedimethylene"; line 7 insert --terephthalate)--; line 75, insert--2. Poly( +-isopropylidenebisphenoxyethylo -tetramethyleneterephthalate)--.

Column 3, line 6, delete --phthalate)-- line &5, "ventions" should read"ventiotf; line #6, insert --A. Arylamine photoconductors includingsubstituted and unsubstituted arylamines, diarylamines, nonpolymeriotriarylamines and polymeric triarylamines such as those described in U.S. Patents 3,2 +O,597 and 3,l80,730.-- line 56, butryl should readbutyryl".

Column line 2, before alkoxy" insert --an--- line 2 "nitrate should readnitro"; line 7 l,l,l--triarylakanes should read "1,1 ,l-triarylalkanes";line 10, "moeties should read "moieties"; line Q0, groups, should readgroup,

F22 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Paz m; N3,6l5, IO6 Dated October 26, 1971 Inventor(s) Stewart ll 2 Q It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 4, line 50, in formula, I O is not printed H --CH=CH--C-Rproperly in the patent.

Column 5, line 29, delete "nucleus and 8nucleus; 1967,"; line 65, "on"should read "one".

Column 6, line 52, "(CH=CH) should read"-(CH=CHJ- Column 7, line 55,"material" should read "materials"; line 59, "groups" should read"group".

Column 8, line 1, "hydroxyl" should read "hydroxy".

Column 10, line 1, before the first "atom" insert --an oxygen atom or asulfur atom; J can be any of the substituents set forth above for E G Land Q and in addition can be when taken with E, an oxygen--- line EA"naphthylmaine" should read naphthylamine"; line 33,"polydecamethylentriphenylaimne" should read"polydecamethylentriphenylamine"; line 34,

"plly-N- )h-vinylphenyl)diphenylamine" should readpoly-N-(Q-Vinylphenyl)diphenylamine"; line 39, i, bis(diethylamino)-2,should read "LI, '4"-bis(diethylamino)-2, line 51, "4',4"-bis(dimethylmaino)"should read "4' ,4"- bis(dimethylamino); line 70,b 4' (n-amyloxy)chalcone" should read 5H '-bis(n-amyloxy)chalcone".

P040551 UNITED STATES PATENT OFFICE m CERTIFICATE OF CORRECTION PatentNo. 3 ,615 ,'-+O6 Dated October 26 197].

Inventor(s) Stewart H. Merrill 3 It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 10, line 7 4, insert I'-dipheny1aminocha1cone--; line 75, insert+'-dimethylaminocha1cone--; line 76 insert--bis-[5-(5I-L-dibenzo[a,d7cycloheptenyl7ether--.

Column 11, line 2, "dioarbomethoxyl-" should read "dicarbomethoxy-";line 14, "dimenthylamino-" should read "dimethylamino-; linel9,"cycloheptatrien" should read "cycloheptatriene"; line 31,"NSfuryl-N-(Z-methyl- +hydroxypenyl)" should read'N--3-f\.1".."yl-N-(Z-meth l- -I- hydroxyphenyl)"; line 35,"tolyhydrazine should read "tolylhydrazine".

Column 12 line 18 "propen-lol" should read "propen-l-ol"; line 7"3,150,615" should read "3,250,615"; line 75, "5,lO,dix0xo-4a, shouldread "5,lO,dioxo-4a,".

Column 13, line 22, "of" appearing second time in line should read "or";line 33, "give" should read given".

Column l I, line 3, "or" should read "on".

Column 15 line 20, "trimetylene" should read "trimethylene"; line 5 4,delete 3O.

P0-1050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent3,6l5, +O6 Dated October 26, 1971 Inventor) Stewart H. Merrill 4 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 16, in claim 1, the portion of formula B,

EIH -CH -C- should read {CH -CH -O- Column 17, in claim the portion offormula B CH CH l3 l3 -O- should read -C- 1 I CH CH Column 17 in claim5, the portion of formula (21) -C should read -C- 73 UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,6lS IO6 DatedOctober 26, 1.971

Inventor(s) Stewart Merrill 5 It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 18, line 25 of claim ll, "5" should read line 28 of claim 12, "5"should read "4''; line 31 of claim 13, "5" should read I"; line 32 ofclaim 13, "isopropylidenebispheno ry-" should read"isopropylidenebisphenoxyethyl-"; line +8 of claim 15, "tetreamthylene"should read "trimethylene".

Signed and sealed this 13th day of March 1973.

LEAL) test:

WARD M.I-LI3TCHER,JR. ROBERT GOTTSCHALK testing Officer Commissioner ofPatents

2. The electrophotographic element of claim 1 wherein Z is selected fromthe group consisting of a. a straight chain alkylene hydrocarbonradical, b. an oxydialkylene radical, c. an alkylene bis(oxyalkylene)radical, d. a cycloalkylene hydrocarbon radical, e. a branched chainalkylene hydrocarbon radical, f. a thiadialkylene radical and g. analkylene bis(thiaalkylene) radical.
 3. The electrophotographic elementof claim 1 wherein the photoconductive composition contains a sensitizerselected from the group consisting of cyanine and pyrylium dye salts. 4.An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising an organicphotoconductor, a sensitizer and a binder for said photoconductor andsensitizer, comprising a random, linear copolyester having repeatingunits of
 5. The electrophotographic element of claim 4 wherein Z isselected from the group consisting of
 6. The electrophotographic elementof claim 4 wherein the sensitizer is selected from the group consistingof carbocyanine, pyrylium, thiapyrylium and selenapyrylium dye salts. 7.The electrophotographic element of claim 4 wherein the organicphotoconductor is 4,4''-benzylidenebis(N,N-diethyl-m-toluidine).
 8. Theelectrophotographic element of claim 4 wherein the binder has 20 percentto 80 percent of repeating unit A.
 9. The electrophotographic element ofclaim 4 wherein the binder has 30 percent to 60 percent of repeatingunit A.
 10. The electrophotographic element of claim 4 wherein thebinder is poly(4,4''-isopropylidenebisphenoxyethyl-co-trimethyleneterephthalate).
 11. The electrophotographic element of claim 5 whereinthe binder ispoly(4,4''-isopropylidenebisphenoxyethyl-co-tetra-methyleneterephthalate).
 12. The electrophotographic element of claim 5 whereinthe binder is poly(4,4''-isopropylidenebisphenoxyethyl-co-pentamethyleneterephthalate).
 13. The electrophotographic element of claim 5 whereinthe binder ispoly(4,4''-isopropylidenebisphenoxy-co-oxydiethylterephthalate).
 14. Anelectrophotographic element comprising a support having coated thereon aphotoconductive composition comprising 10 to about 60 weight percent of4,4''-benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4''-isopropylidenebisphenoxyethyl-co-trimethylene terephthalate)as a binder for said photoconductive composition.
 15. Anelectrophotographic element comprising a support having coated thereon aphotoconductive composition comprising 10 to about 60 weight percent of4,4''-benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4''-isopropylidenebisphenoxyethyl-co-tetreamthyleneterephthalate) as a binder for said photoconductive composition.
 16. Anelectrophotographic element comprising a support having coated thereon aphotoconductive composition comprising 10 to about 60 weight percent of4,4''-benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4''-isopropylidenebisphenoxyethyl-co-pentamethyleneterephthalate) as a binder for said photoconductive composition.
 17. Anelectrophotographic element comprising a support having coated thereon aphotoconductive composition comprising 10 to about 60 weight percent of4,4''-benzylidinebis(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor andpoly(4,4''-isopropylidenebisphenoxyethyl-co-oxydiethyl terephthalate) asa binder for said photoconductive composition.